Ferro silicon 70 | Si >= 70 Deoxidizer and alloy additive for steelmaking and casting

Ferrosilicon 70 (FeSi70) is a highly versatile alloying additive in the metallurgical industry. Its core functions focus on deoxidation and alloying strengthening in steelmaking. With its advantages of "balanced silicon content and controllable cost", it is suitable for the production of mainstream steels such as ordinary carbon steel and low alloy steel. The precise control of its addition amount directly affects the purity of molten steel and the mechanical properties of steel.

 Composition range: Si 68%-72%, Fe 25%-28%, impurities Al≤1.5%, S≤0.05%, P≤0.04%, C≤0.2%;
 Physical properties: Melting point 1250-1280℃, density 6.9-7.1g/cm³, silvery-gray lumps (10-50mm) or granules (1-10mm), hard and brittle texture, strong reducing properties at high temperatures;
 Core advantages: Balanced cost-effectiveness, stable deoxidation efficiency, cost 8%-12% lower than FerroSilicon 75, suitable for large-scale production.

(1) Steelmaking Deoxidation: Core Functions and Quantitative Effects

FeSi70% is the mainstream deoxidizer in the steelmaking industry. It achieves deoxidation through the reaction of silicon with oxygen in molten steel, while simultaneously optimizing the purity of molten steel:

Core Reaction Mechanism:

Si + 2FeO → SiO₂ + 2Fe (spontaneous reaction in molten steel at 1500-1600℃). The density of the generated SiO₂ is much lower than that of molten steel, making it easy to float and be removed with the slag;

Conventional Addition Amount:

0.3%-0.8% of the molten steel mass, which can reduce the oxygen content of molten steel from 80-100ppm to 35-55ppm, achieving a deoxidation efficiency of 45%-65%;

Comparative Advantages:

Compared with FerroSilicon 65, the deoxidation efficiency is increased by 10%-15%; compared with FeSi 75%, the cost is reduced. 8%-12%, and the deoxidation effect meets the requirements of ordinary steel and low alloy steel;

(2) Alloying effect: performance enhancement and quantitative improvement

FeSi alloy 70 enhances the mechanical properties of steel through the solid solution strengthening effect of silicon, and is suitable for the production of low alloy steel and structural steel:

Core strengthening mechanism:

Silicon atoms are incorporated into the ferrite lattice, causing lattice distortion, hindering dislocation movement, and at the same time refining the grains, thereby improving the strength and hardness of the steel;

Low alloy structural steel (such as Q355):

Adding 0.2%-0.5% FerroSilicon alloy 70%, controlling the silicon content in the steel to 0.3%-0.6%, the tensile strength increases from 345MPa to 380-400MPa, the yield strength increases by 10%-15%, and the impact toughness (-20℃) remains ≥60J/cm²;

Ordinary carbon steel (such as Q235):

Adding 0.3%-0.4% FerroSilicon alloy 70, the tensile strength increases from 235MPa to 270-290MPa, meeting the strength requirements of building and mechanical structural components.

(1) Steelmaking Industry: Mainstream Deoxidation and Alloying Raw Material

Suitable Steel Grades: Ordinary carbon steel (Q235, Q255), low-alloy high-strength steel (Q355, Q420), welded structural steel (Q345R), etc.;

 Process Adaptation:

Converter Steelmaking: Added during tapping (10-50mm blocky), 0.4%-0.8%, utilizing turbulent mixing of molten steel for thorough deoxidation reaction;
Electric Furnace Steelmaking: Added in the later stage of furnace charge melting (1-10mm granular), 0.3%-0.6%, combined with argon stirring to improve the uniformity of molten steel composition;

(2) Foundry Industry: Inoculant and Flowability Improver

FeSi70 In casting, it is mainly used in the production of gray cast iron and ductile iron to improve the quality of castings:

 Inoculant application:

Mechanism of action: Promotes graphitization precipitation, avoids white iron formation tendency, and refines graphite grains and matrix structure;

Quantitative effect: With the addition of 0.2%-0.5% granular FeSi70 (1-3mm) (gray cast iron), the tensile strength of castings increases from 200MPa to 250-280MPa, and the porosity defect rate decreases from 0.8% to 0.2%;

 Improved fluidity:

Mechanism of action: Silicon element reduces the viscosity of molten iron, improves fluidity, and reduces defects such as "insufficient pouring" and "cold shut";

Quantitative effect: With the addition of 0.3%-0.4% FeSi70, the fluidity of molten iron is improved by 15%-20%, which is suitable for the production of castings with complex structures;

(3) Other application scenarios

Ferroalloy production: As a reducing agent, it assists in the production of alloys such as ferromanganese and ferrochrome. The addition amount is 1%-2%, which improves the alloy recovery rate. 5%-8%;
Recycled steel smelting: Replenish silicon loss in recycled steel, adding 0.5%-0.7% to ensure steel composition meets standards and reduce scrap rate;

(1) Core selection logic

Steel grade/casting requirements:

Select FeSi70 for ordinary steel and conventional casting, and FeSi75 (higher deoxidation efficiency) for high-end steel and precision casting;

Process compatibility:

Select blocky (10-50mm) for converter/electric furnace steelmaking, and granular (1-3mm) for casting inoculation;

Cost balance:

FeSi70 has the best cost performance. If the steel grade has strict requirements for impurities (e.g., Al≤0.8%), low-alumina FeSi70 can be selected.

(2) Parameter comparison table for different scenarios